At present, commonly used microscopes often have a controller capable of controlling the microscope. Controllable parameters include, for example, an illuminating laser beam of the microscope, individual wavelengths or wavelength bands of the illuminating laser beam, controllable beam splitters in the optical path of the microscope, and the detection device. Some of the parameters remain constant for a relatively long period of time, whereas other parameters change very quickly.
One particular application is in confocal microscopes. In confocal microscopes, a sample is typically scanned in a meander pattern along image lines. To this end, an illuminating laser beam is directed onto the sample, and the detection light beam coming from sample is detected by a detection device. The detection light beam may be produced by reflection of the illuminating laser beam at the sample or by fluorescence effects. When a sample is scanned unidirectionally, the detection light beam is detected only during movement of the illuminating laser beam in one direction. When scanning is performed bidirectionally, the detection light beam is detected during movement of the illuminating laser beam in both directions. Depending on the design of the confocal microscope, up to 8,000 lines per second (and more) can be scanned in unidirectional mode, and up to 16,000 lines per second (and more) can be scanned in bidirectional mode.
When living samples are examined, care must be taken not to deliver too much energy to the sample during a scanning operation in order not to destroy the sample. Therefore, so-called regions of interest (ROI) are defined in sample regions which are expected to be of interest and in which the illuminating light beam is activated. A controller activates the illuminating laser beam based on the position of the image points to be illuminated. To this end, control information is made available to the controller, on the basis of which the controller controls a parameter of the microscope, in this case the illuminating laser beam.
A circuit for controlling a microscope, as known in the prior art, is schematically shown in FIG. 1. The circuit of FIG. 1 has a slow memory in the form of, for example, a double data rate random access memory (DDR-RAM). A data loader B sends an address to slow memory A, requesting control information stored at that address, and receives control information from slow memory A. This control information is stored in a fast memory C, which may be in the form of a hardware register. Fast memory C is typically implemented as a line buffer; i.e., fast memory C contains the control information for all image points of an image line during illumination of the sample. The control information stored in fast memory C can be retrieved by a controller D and used for controlling the microscope. Writing into the fast memory is in principle only possible while it is not being read.
The control information for one image point typically includes a plurality elements. In a confocal microscope marketed by the applicant, 64 individual bits are stored as control information for one image point and evaluated by the controller. One bit may control, for example, whether an illuminating laser beam or an illuminating laser line is on or off at an image point.
During operation of the circuit shown in FIG. 1, the control information for one line is loaded from the slow memory into the fast memory between active phases of two image lines. Generally, the illuminating laser beam is scanned across the sample at a constant velocity within the scan region. When the illuminating laser beam leaves the scan region, the illuminating laser beam is decelerated and returned in the opposite direction on the next image line to the beginning of the scan region. When scanning is performed bidirectionally, the next image line is scanned as the illuminating laser beam is returned across the sample. When the scanning is unidirectional, the laser beam is returned while in the OFF state, the direction is changed, and the next image line is not scanned until the illuminating laser beam moves back. This results in scan pauses between the completion of the scanning of an image line and the repositioning of the illuminating laser beam. These scan pauses are used for loading control information into the fast memory.
The prior art circuit is problematic because large volumes of data must be loaded from the slow memory into the fast memory within a short period of time. To this end, the individual elements of the circuit must be sufficiently fast in order for the loading operation to be completed when the loaded control information is to be accessed at the beginning of the next image line. If the volume of data to be loaded increases, for example, because the control information to be handled by a channel is not just binary information, but rather is control information having a resolution of several bits, the prior art circuit fails. If the speed of the circuit cannot or should not be further increased, the scanning speed must be reduced; i.e., the time for the loading operation must be increased by longer pauses between the scanning of two image lines.